On Sat, Jul 26, 2025 at 02:24:51PM +0200, Hans de Goede wrote: > Hi Kees, > > On 24-Jul-25 10:08 AM, Kees Cook wrote: > > When gmin_get_config_var() calls efi.get_variable() and the EFI variable > > is larger than the expected buffer size, two behaviors combine to create > > a stack buffer overflow: > > > > 1. gmin_get_config_var() does not return the proper error code when > > efi.get_variable() fails. It returns the stale 'ret' value from > > earlier operations instead of indicating the EFI failure. > > > > 2. When efi.get_variable() returns EFI_BUFFER_TOO_SMALL, it updates > > *out_len to the required buffer size but writes no data to the output > > buffer. However, due to bug #1, gmin_get_var_int() believes the call > > succeeded. > > > > The caller gmin_get_var_int() then performs: > > - Allocates val[CFG_VAR_NAME_MAX + 1] (65 bytes) on stack > > - Calls gmin_get_config_var(dev, is_gmin, var, val, &len) with len=64 > > - If EFI variable is >64 bytes, efi.get_variable() sets len=required_size > > - Due to bug #1, thinks call succeeded with len=required_size > > - Executes val[len] = 0, writing past end of 65-byte stack buffer > > > > This creates a stack buffer overflow when EFI variables are larger than > > 64 bytes. Since EFI variables can be controlled by firmware or system > > configuration, this could potentially be exploited for code execution. > > > > Fix the bug by returning proper error codes from gmin_get_config_var() > > based on EFI status instead of stale 'ret' value. > > > > The gmin_get_var_int() function is called during device initialization > > for camera sensor configuration on Intel Bay Trail and Cherry Trail > > platforms using the atomisp camera stack. > > > > Reported-by: zepta <z3p...@gmail.com> > > Closes: > > https://lore.kernel.org/all/capbs6koqym7fmdpwouxtexsoe44x4h3f8fw+y_qwq6e+odm...@mail.gmail.com > > Fixes: 38d4f74bc148 ("media: atomisp_gmin_platform: stop abusing efivar > > API") > > Signed-off-by: Kees Cook <k...@kernel.org> > > Thanks, patch looks good to me: > > Reviewed-by: Hans de Goede <ha...@kernel.org> > > I've already send an atomisp pull-request for 6.17 out > and this is already in media-committers/next now and > the media subsystem is typically not good in merging > fixes just before the merge window. > > Kees, the file touched here is unchanged in > media-committers/next vs Linus' latest master, can you > send this fix to Linus yourself ?
I apologize; this slipped through the cracks. Shall I take it for -rc2, or do you want to snag it? -Kees -- Kees Cook
