RFE: minimze ebitmap serialization #66
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stephensmalley
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May 2, 2024
Florian reported the following kernel NULL pointer dereference issue on a BCM7250 board: [ 2.829744] Unable to handle kernel NULL pointer dereference at virtual address 0000000c when read [ 2.838740] [0000000c] *pgd=80000000004003, *pmd=00000000 [ 2.844178] Internal error: Oops: 206 [SELinuxProject#1] SMP ARM [ 2.848990] Modules linked in: [ 2.852061] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.8.0-next-20240305-gd95fcdf4961d SELinuxProject#66 [ 2.860436] Hardware name: Broadcom STB (Flattened Device Tree) [ 2.866371] PC is at brcmnand_read_by_pio+0x180/0x278 [ 2.871449] LR is at __wait_for_common+0x9c/0x1b0 [ 2.876178] pc : [<c094b6cc>] lr : [<c0e66310>] psr: 60000053 [ 2.882460] sp : f0811a80 ip : 00000012 fp : 00000000 [ 2.887699] r10: 00000000 r9 : 00000000 r8 : c3790000 [ 2.892936] r7 : 00000000 r6 : 00000000 r5 : c35db440 r4 : ffe00000 [ 2.899479] r3 : f15cb814 r2 : 00000000 r1 : 00000000 r0 : 00000000 The issue only happens when dma mode is disabled or not supported on STB chip. The pio mode transfer calls brcmnand_read_data_bus function which dereferences ctrl->soc->read_data_bus. But the soc member in STB chip is NULL hence triggers the access violation. The function needs to check the soc pointer first. Fixes: 546e425 ("mtd: rawnand: brcmnand: Add BCMBCA read data bus interface") Reported-by: Florian Fainelli <[email protected]> Tested-by: Florian Fainelli <[email protected]> Signed-off-by: William Zhang <[email protected]> Signed-off-by: Miquel Raynal <[email protected]> Link: https://lore.kernel.org/linux-mtd/[email protected]
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Maybe with one of the next kernel policy format changes one could minimize the ebitmap serialization.
Currently each serialized ebitmap contains the mapsize (which could be included once in the policy header) and the hightbit (which can be computed from the highest node plus the mapsize).
For example the current Reference policy compiles to a 1.9M file with 6970 ebitmaps, so
6970 * 2 * 4Byte - 4Byte(~ 2.9%) can be saved.The text was updated successfully, but these errors were encountered: